Researchers have replaced toxic photosensitive compounds with natural dyes, allowing the construction of functioning 3D printed lungs.
Living organs include complex networks of blood vessels that provide oxygen and nutrients and remove waste – networks that are essential for survival. The need for this complex network has been a challenge for researchers attempting to construct living organs using 3D printing technology.
In the human lung, for instance, blood and air continuously flow and interact without coming in direct contact. This interaction, which involves blood vessels as narrow as 300 micrometers in diameter, is essential for proper functioning. To construct a printed 3D network of these vascular channels surrounding air sacs, researchers at Rice University and the University of Washington first used a liquid hydrogel solution containing photosensitive compounds that, when exposed to blue light, solidifies. 2D images of layers of the 3D vessel network were projected one at a time, ultimately leading to a complex and independent 3D structures across a soft scaffold.
Unfortunately, the photosensitive compounds used in this system are toxic to living tissue, so the 3D lung could not function.
Their solution was to substitute the toxic compounds with food dyes (synthetic and natural) that have been approved for human consumption. The dyes investigated included curcumin, the yellow-orange component in turmeric used to color butter, cheese and mustard and tartrazine, or yellow dye #5, which is used to color most other foods from macaroni and cheese to soft drinks and candies.
The dyes served as effective photo absorbers, allowing the construction of complex architectures of human vasculature in which living cells could survive. The researchers showed that in one of the 3D-printed lung-like structures a little smaller than a penny, the vessels were able to handle blood blow and rhythmic breathing motions of inhaling and exhaling air. In addition, the red blood cells took up oxygen as they moved past the air sacs in the structure.
Houston-based startup Voluemtric will be commercializing the bioprinting and bio-ink technologies developed by the researchers, who are also making the data available through open-source files.
